Purpose: The objective of this study was to investigate the effects of different microthread designs and implant-abutment connection configurations of scalloped implants on stress distribution in bone using three-dimensional finite element analysis. Materials and Methods: Three different designs of scalloped implants (two different microthread designs and one without microthreads) with two different connection systems and two flat-top implants with similar connection systems were compared in a bone model that mimicked the anterior maxilla. Vertical and oblique (30-degree) loading with 100 N of force was applied to eight models. Peak stress levels and the distribution of stress were observed. Results: The stress pattern of scalloped implants was distinctively different from that observed on flat-top implants. Scalloped implants showed peak stresses in the proximal cortical bone as well as in the buccal and palatal cortical bone, whereas flat-top implants showed peak stresses mainly in the buccal and palatal cortical bone and limited stress in the proximal bone. The scalloped implant without microthreads and a conical platform-switched connection demonstrated the lowest peak stress levels. The scalloped implant with a straight platform connection generally showed peak stress that was two to three times higher than that seen in the conical platform-switched model. Conclusions: Peak stress levels in scalloped implants varied with microthread designs, connection configurations, and the direction of loading. The conical platform-switched connection seemed more important for a scalloped implant than the microthread design in reducing loading stresses exerted on the surrounding bone. Scalloped implants without microthread and a with a conical platform-switched connection or closed microthreads and a conical platform-switched connection showed consistently lower buccal bone stress than the flat-top implants in areas where the bone had a sloping and scalloping shape. INT J ORAL MAXILLOFAC IMPLANTS 2012;27:e29–e38.

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